Now, using the Hubble Space Telescope, scientists have confirmed the presence of water and also detected methane.

Planets outside our solar system, called exoplanets, are so far away that scientists can't obtain images clear enough to separate the planet from its star.

So to study HD 189733b, the team used an instrument aboard Hubble called a spectrometer, which breaks up light passing through a planet's atmosphere into different bands.

"The big news is that this is the first detection of an organic in an exoplanet atmosphere," said lead study author Mark Swain, a researcher at the Jet Propulsion Laboratory and the California Institute of Technology.

The study appears in this week's issue of the journal Nature.

Transiting Planet

HD 189733b is a transiting planet, meaning it periodically passes in front of its star as viewed from Earth.